The Door Holder: A Notched Bar the Knob Unlocks

Dorsey's device is for "securing it (the door) open at any desired angle, and by which there is no possible chance of its being forced to by the draft or other cause, to prevent its accidental slapping and risking the breaking of the glass therein", as in "inner hallway-doors and store and office doors." A case A on the door guides a bar B. The bar's rear end is pinned to a rod C whose axis turns in plates on a base on the frame, with a spring c coiled round it, "by which, when the bar B is free to slide, upon opening the door, the latter will be automatically closed." A bell-crank lever D is linked by an arm d to a collar E on the knob spindle; its other end carries a pin g that can "fall by gravity into its notch" k in the bar. A slot f in the collar lets the knob draw back the latch without disturbing the holder. "Upon turning the knob to open the door, it will elevate and disengage the pin g"; on releasing it, the pin falls into the coincident notch and holds the door. "A reverse movement of the knob by the hand is the only means by which the retaining or holding pin g can be retracted". A prop l holds the lever up "when the holding device is not needed or the weather may be too cool for the holding of the door open."

On a cupboard door hung on butt hinges, screw a short length of aluminium bar as the slide, running in two small brackets on the door's top edge; file notches along it every 15 mm. Link its end to the frame with a stiff wire rod pivoted on a screw. Hinge a small lever on the door with a pin that drops into the notches by its own weight. Open the door and let the pin fall: count the positions it holds in, and measure their angle with the protractor against the notebook. Push the door with the spring scale at its edge to see how much it takes to force it. Then replace one hinge with a spring hinge so the door closes itself when the pin is lifted.

**Osbourn Dorsey** of Washington, D.C., filed US 210,764 on 8 June 1878; it is dated 10 December 1878. Its claims cover the rod, notched slide and pinned lever, the slotted knob-spindle collar that works the lever, and the prop. **Honest limits.** The distances, pressures and pin size in the notebook are examples. Doorknobs existed long before 1878.